Late Pleistocene Paleoclimatic And Paleoenvironmental Evolution Of The Basins Of Northwest Hebei Mountains And Landform Of Western Hebei, Taihang Mountains

Nihewan Basin located in the basin of Northwestern Hebei mountains, where a completeand complex fluvial–lacustrine sediment belonging to standard Quaternary strata can be foundand a large number of animal fossils and Paleolithic site has been found and excavated.Houjiayao site is one of the argued Paleolithic sites in Nihewan Basin because of the age.Shuilian cave site was discovered in2009locates in the Landform of Western Hebei inTaihang Mountains.Sediment samples were derived from natural palaeo-soil profile in Haojiayao site and ashlayers in Shuilian cave site for pollen and charcoal analysis. Based on the pollen and charcoaldata analysis, the author recovered the revolution of paleoclimatic and paleoenvironmentalevolution in the middle and north of Taihang Mountains during the Late Pleistocene epoch,and reconstructed the paleo climate and environment when ancient human lived in.Palynology analysis of Haojiayao Site shows that the p poller assemblages weredominated by conifer,such as Pinus and Pica, indicating that the vegetation was mainly mixedconefer-broadleaves forest and the climate was cold and humid in MIS5b(90-80ka);thepercentage of conifer poller was reduced and shrubs was markedly increased that displays thevegetation was a forest steppe with the climate was warm and dry in MIS5a(80-70ka); thepercentage of conifer pollen increased remarkably and the herbs reduced points that the mixedconifer-broadleaves forests vegetation covered the study site with the cold and humid climatein MIS4(70-60ka), which was also the period of the Houjiayao human to live; the pollenpercentage of herbs accounted advantage, such as Artemisia、Chenopodiaceae、Poaceace andRanuculaceae etc, broad-leaves trees pollen (Quercus、Ulmaceae、Carpinus and Betula) wasless and the conifer pollen decreased obviously, that indicates the vegetation was a foreststeppe and the climate has changed to warm and humid in MIS3(60-50ka,40-30ka); thepercentage of Pinus somewhat gone up, the herbaceous reduced a little, the vegetation was aforest steppe and the climate is cold and dry in colder of the stage MIS3(50-40ka).Charcoal analysis of Haojiayao site displays micro-charcoal was abundant in, especiallyin MIS5, indicating that regional fire happened, the site was located in the frontal depression of Liyi river’s piedmont alluvial fan in that time, the river flow slowly, and the charcoal wascarried by water and deposited nearby the site; the concentration of charcoal reduced at alarger amount and the climate became to cold and wet again, which shows the frequency andintensity of the fire decreased in MIS4; the climate changed to warm and dry, but the contentof charcoal was lower than the other two stages in MIS3, the change of depositionalenvironment is one of the reasons.There was a remarkable climate change from the former succession between cold-wetand warm-dry to the later between cold-dry and warm-wet after the years of50-40ka BP. Theancient residents of Houjiayao human lived in the glacial period(MIS4) with cold climatewhen there was mixed needle broad-leaves forests dominated by Pinus and Picea and a stablewater body around and nearby the site. The feasible natural environment was suitable for notonly animals to live but also for human beings to capture food. The ancient Houjiayaoresidents had have theabilities to adapt cold weather, because food is more important in coldclimate, especially in the Paleolithic period with low productivity.The pollen spectra of Shuilian cave site shows it is warm and wet when the ancienthuman lived. The dating results of the bones shows the ancient human lived in the stageMIS3(the interstadial of Last glaciation) and the caves provided them with refuge: from37000cal a BP to36700cal a BP, vegetation around the cave was dominated by broad-leavesforests, for example Cotinus、Juglandaceae、Betula、Carpinus and a large of shrubs (Spiraea)and herbaceous, such as Artemisia、Poaceace and Chenopodiaceae etc, shows that the climatewas warm and humid. From36700cal a BP to32300cal a BP, the percentage ofChenopodiaceae increased slightly with Artemisia reduced, indicating that the climate waswarm and dry; from32300cal a BP to30000cal a BP, Artemisia inceared again andChenopodiaceae reduced, the climate was warm and wet.We thought the change of charcoal concentration of Shuilian cave site may be display thechange of using fire for the ancient Shuilian cave residents’ living, because of enclosedenvironment about cave.